The correct answer is that the Lambda authorizer’s cached results are still valid, so the old IAM policy is being applied. When API Gateway invokes a Lambda authorizer, it caches the returned policy document for the configured TTL—here, 300 seconds—meaning subsequent requests within that window reuse the cached decision, even if the underlying IAM policy for the authorizer’s execution role has been updated. This scenario tests your understanding of how authorizer caching interacts with IAM changes, a common trap on the AWS Certified Developer Associate DVA-C02 exam where candidates mistakenly think updating the role or redeploying the API immediately refreshes permissions. The key insight is that the authorizer result, not the role itself, is cached; the IAM update is instantaneous for the role, but the cached “deny” from the old policy persists until the TTL expires or you manually invalidate the cache. Memory tip: think of the authorizer cache as a stubborn bouncer who keeps using last week’s guest list—you have to wait for the list to expire or clear it yourself.
DVA-C02 Troubleshooting and Optimization Practice Question
This DVA-C02 practice question tests your understanding of troubleshooting and optimization. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A developer is using Amazon API Gateway with a Lambda authorizer to protect a REST API. The authorizer is configured with a TTL of 300 seconds. After updating the IAM policy attached to the authorizer's execution role, some users still receive 403 Forbidden errors for requests that should be allowed. What is the MOST likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The authorizer's cached results are still valid, so the old policy is being applied.
Option C is correct because the Lambda authorizer result is cached for 300 seconds, so old permissions are enforced until the cache expires. Option A is wrong because the authorizer function itself does not have an execution timeout issue. Option B is wrong because the IAM policy update is immediate for the role, but the authorizer result is cached. Option D is wrong because the deployment does not affect authorizer caching.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
The Lambda authorizer function has a timeout that prevents it from evaluating the new policy.
Why it's wrong here
The authorizer timeout is separate and unlikely to cause a 403; it would cause 500.
✓
The authorizer's cached results are still valid, so the old policy is being applied.
Why this is correct
Caching causes the authorizer to return previous decisions until the TTL expires.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The IAM policy update has not propagated to all regions.
Why it's wrong here
IAM updates are global and propagate quickly.
✗
The API Gateway endpoint was not redeployed after the policy change.
Why it's wrong here
Redeployment is not required for authorizer changes; cache invalidation is needed.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
What to study next
Got this wrong? Here's your next step.
Identify which DVA-C02 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Troubleshooting and Optimization — This question tests Troubleshooting and Optimization — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The authorizer's cached results are still valid, so the old policy is being applied. — Option C is correct because the Lambda authorizer result is cached for 300 seconds, so old permissions are enforced until the cache expires. Option A is wrong because the authorizer function itself does not have an execution timeout issue. Option B is wrong because the IAM policy update is immediate for the role, but the authorizer result is cached. Option D is wrong because the deployment does not affect authorizer caching.
What should I do if I get this DVA-C02 question wrong?
Identify which DVA-C02 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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